1. Field of the Invention
This invention pertains to valves.
2. Description of the Prior Art
In drip irrigation systems, such as used in orchards and other locations, many lines are connected to a water main and are intended to provide a metered flow of water to various trees or other plant life to accomplish slow irrigation. It is important to control the flow in the various fluid lines in order that each specimen will receive the right amount of water, not too much and not too little. This requires a large number of valves for controlling the flow. Because of the number of valves used, they should be low in cost to keep the price of an irrigation system within reason. The valves should be easy to handle, noncorrosive, durable, reliable, and readily adjustable. Valves of the prior art do not, in any one design, meet all of these criteria. Frequently, valves of brass have been used which are relatively costly and somewhat complex in construction.
Plastic valves have been made for other purposes, but have not been adapted as low cost valves for drip irrigation systems. In particular, when plastic valves are of molded construction, distortion results from shrinkage of the material as it cools during the molding process. This may cause the surface of the valve body engaged by the valve member to be out of round so that the valve member will not seal against it. This is an especially troublesome problem where fluid pressures are relatively high. If the valve body is machined to provide an accurately contoured surface, the cost of the valve is increased greatly.